Ornamental design for a boot



FIG. 1 is a top plan view of a boot showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a right side elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a rear elevation view thereof; and

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a boot, substantially as shown. 